Hand-holdable impacting tools of the same general character as the present invention are well-known and are presently widely used in various fields. Typically, these impacting handpiece tools are employed for providing repeated hammering to a particular work piece, such as required in the jewelry and electronics field for light riviting, peening, stone setting, etc., as well as for providing controlled, repeated tamping of material such as an amalgam, as employed by dentists in the filling of cavities.
Although portable, hand-holdable impacting tools have been widely used, these prior art impacting tools are expensive to manufacture and are generally incapable of inexpensive mass production. These deficiencies are due to the precision manufacturing requirements imposed upon various components of these prior art tools.
All impacting tools incorporate a system which converts rotary motion into axial motion, and generally comprise the same basic construction. Typically, the rotary motion is provided by an elongated, flexible, shielded cable which incorporates a central rotating shaft member, similar to the cables employed in speedometers.
The shielded cable is securely mounted within the housing of the impacting tool, and drivingly connected to a cam follower mounted to the distal end of an internal rotating spindle. The cam follower is positioned in abutting sliding frictional contact with a substantially helical cam surface, which is formed on an axially movable cam member. The cam member is spring loaded for its axial movement in one direction, with the cam follower's movement along the cam surface forcing the cam member in the opposite direction.
The cam surface incorporates a sloped or ramped portion which causes the cam follower to move the cam member against the spring force and then, when the cam follower reaches the end of the cam's ramped zone, the spring forces the cam member in the opposite axial direction. This forward and backward axial motion is continuously repeated, causing the operating end of the impacting tool to move in the same manner. Since the rotating cam follower and spindle continuously and rapidly rotate about their axis of rotation, the operating end of the impacting tool achieves a plurality of rapid forward and rearward cycles, attaining the desired repeated, continuous hammer-like impacts on the workpiece.
Although many alternate structures have been developed for portable, hand-holdable, impacting tools, all of these constructions have suffered from the consistent use of expensive cam surfaces which must be manufactured with very precise slope requirements within stringent tolerances. As a result, this particular component part is extremely difficult to fabricate and, consequently, extremely expensive.
In addition, some of these prior art impacting tools suffer from the lack of some means to prevent the cam member and its associated anvil member from rotating due to the rotational motion induced by the cam follower. Rotation of the anvil and cam surface is undesirable, since it causes the cycling pattern of the anvil tip to change repeatedly or, possibly, never occur.
Some prior art devices do incorporate means for preventing this rotation. However, such anti-rotation means generally comprise pin members which require expensive machining of both the pin as well as the pin-receiving hole, thereby substantially increasing the cost of the impacting tool.
Consequently, it is the principle object of the present invention to provide a portable, hand-holdable impacting tool which incorporates an inexpensively produced and easily installed spring loaded cam surface.
Another object of the present invention is to provide a portable, hand-holdable impacting tool having the characteristic features described above which also incorporates an anti-rotation system cooperatively associated with the anvil which is inexpensively manufactured and quickly and easily installed.
Another object of the present invention is to provide a portable, hand-holdable impacting tool having the characteristic features described above which is inexpensively manufactured and provides fail-safe, dependable, and continuous operation.
Other and more specific objects will in part be obvious and will in part appear hereinafter.